The invention concerns a frame cladding for the thermal insulation of windows having a window frame in a masonry opening and a sash frame incorporating a window pane of insulating glass.
The increasingly rigorous requirements regarding the insulating performance of windows and which have to be fulfilled according to the current or anticipated statutory regulations are met by glazing but not by the materials of frame material group 1 (wood/plastic) generally used for single windows.
The best insulating glazing already achieves a thermal transmittance value (U-value) of 0.4 Wm2K, while wood or plastic can only achieve a U-value of 1.3 Wm2K. A new Thermal Insulation Act due to come into force shortly will call for a Uw-value of 1 for the complete window, which is not feasible with the technology used hitherto.
A facade element with a window opening is known from DE-A-25 18 800. This facade element has an inner and an outer skin of sheet metal with insulation material filling the cavity between these two skins. This applies not only to the area of the window opening but indeed to the whole facade element. A step is formed in the area of the window opening which is an integral part of the facade element. This step extends over the sash frame of the window and runs parallel to this and the plane of the pane of glass. A permanently elastic gasket, whose lips make contact with the pane of glass, is attached to the end of this step. When the facade element is used as an external cladding and insulating component, then it is fixed directly to a wall. In this case the facade element is designed with a constant thickness without a step in the area of the window opening.
It is the object of the invention to devise a frame cladding for improving the thermal insulation of windows.
This task is solved with the aforementioned frame cladding in that the frame cladding consists of a twin-walled casing made from weatherproof material, whereby the cavity formed between the inner and outer walls is filled with a thermal insulation material, said casing covers the outside of the window frame and sash frame, and at the end of the casing not adjacent the masonry the rainwater drip of the sash frame is bent inwards to overlap the window pane and make contact with said window pane via a permanently elastic gasket fitted to its end.
The arrangement according to the invention covers the edge seal of the insulating glass pane so critical in terms of thermal insulation, and in conjunction with the thermal insulation material enables a Uw-value less than 1 to be easily achieved.
An advantageous arrangement of the invention for a window frame of plastic or metal is to form the frame cladding in one piece with this.
In another embodiment form of the invention, the frame cladding is attached as a separate component to the window frame. Such an arrangement is preferable for use with wooden window frames.
In the embodiment of the invention the permanently elastic gasket is detachable and is inserted into the end of the bent part of the casing, e.g. clipped in with a profile.
Advantageous further forms of the invention result from the remaining, related claims.
A window frame is known from DE-OS 26 21 365 in which the outer face of the window frame is provided with a casing of weatherproof material, the end of which incorporates a permanently elastic gasket which makes contact with the pane of glass. This is intended to improve the sealing of the window but, unlike the invention, not the thermal insulation of the window.